thrombocythemia and thrombocytosis

Thrombocythemia and thrombocytosis are conditions in which your blood
has a high number of blood cell fragments called platelets.

Platelets are made in your bone marrow
along with other kinds of blood cells. They travel through your blood vessels
and stick together (clot) to stop any bleeding that could happen if a blood
vessel is damaged. Platelets also are called thrombocytes, because a clot
also is called a thrombus.

A normal platelet count ranges from 150,000 to 450,000 platelets per microliter
of blood.

Overview

The term "thrombocythemia" is preferred when the cause of the high platelet
count isn't known. The condition is then called primary or essential thrombocythemia.

This condition occurs when faulty cells in the bone marrow make too many
platelets. Bone marrow is the sponge-like tissue inside the bones. It contains
stem cells that develop into red blood
cells, white blood cells, or platelets. What causes the bone marrow to make
too many platelets often isn't known.

With primary thrombocythemia, a high platelet count may occur alone or with
other blood cell disorders. The platelet count can be as low as 500,000
platelets per microliter of blood or higher than 1 million platelets per
microliter of blood. This condition isn't common.

When another disease or condition causes a high platelet count, the term
"thrombocytosis" is preferred. This condition often is called secondary
or reactive thrombocytosis.

In this condition, the platelet count usually is less than 1 million platelets
per microliter of blood. Secondary thrombocytosis is more common than primary
thrombocythemia.

Most people who have a high platelet count don't have signs or symptoms.
Rarely, serious or life-threatening symptoms can develop, such as blood
clots and bleeding. These symptoms mostly occur in people who have primary
thrombocythemia.

Outlook

People who have primary thrombocythemia but no signs or symptoms don't need
treatment, as long as the condition remains stable. Other people who have
this condition may need medicines or procedures to treat it. Most people
who have primary thrombocythemia will live a normal life span.

Treatment and outlook for secondary thrombocytosis depend on its underlying
cause.

What causes thrombocythemia and thrombocytosis?

Primary thrombocythemia

In this condition, faulty stem cells in the bone marrow make too many platelets.
What causes this to happen usually isn't known. When this process occurs
without affecting other blood cells, it's called essential thrombocythemia.

A rare form of thrombocythemia is inherited, i.e., passed from parents to
children.) In some cases, a genetic mutation may cause the condition.

In primary thrombocythemia, the platelets aren't normal. They may form blood
clots, or, surprisingly, cause bleeding when they don't work properly.

Bleeding also can occur because of a condition that develops called von
Willebrand disease. This condition affects the blood clotting process.

After many years, scarring of the bone marrow can occur.

Secondary thrombocytosis

This condition occurs when another disease, condition, or outside factor
causes the platelet count to rise. For example, 35 percent of people who
have high platelet counts also have cancer – mostly lung, gastrointestinal,
breast, ovarian, and lymphoma. Sometimes a high platelet count is the first
sign of cancer.

Unlike primary thrombocythemia, the platelets in secondary thrombocytosis
usually are normal.

Some conditions can lead to a high platelet count that lasts for only a
short time. These include:

Recovery from serious loss of blood

Recovery from a very low platelet count caused by excessive alcohol
use and lack of vitamin B12 or folate

Acute infection or inflammation

Response to physical activity

Who is at risk for thrombocythemia and thrombocytosis?

Primary thrombocythemia

This condition isn't common. The exact number of people who have the condition
isn't known. Some estimates suggest that 1 to 2.5 out of every 100,000 people
have primary thrombocythemia. This number may be low, because most people
who have the condition don't have symptoms. Therefore, they may not know
they have it.

Primary thrombocythemia occurs mostly between the ages of 50 and 70, but
it can occur at any age. For unknown reasons, a higher number of women around
the age of 30 have primary thrombocythemia than men of the same age.

Secondary thrombocytosis

You may be at risk for secondary thrombocytosis if you have a disease, condition,
or factor that can cause it.

This condition is more common than primary thrombocythemia. In two studies
of people with high platelet levels, most people with platelet counts over
500,000 had secondary thrombocytosis.

Signs and symptoms of thrombocythemia and thrombocytosis

Most people who have thrombocythemia or thrombocytosis have no signs or
symptoms. These conditions often are discovered only after routine blood
tests.

People who have primary thrombocythemia are more likely than those who have
secondary thrombocytosis to have serious signs and symptoms.

Primary thrombocythemia

Often, people who have symptoms of primary thrombocythemia only have a mild
form of the condition. The most common symptoms are linked to blood clots
and bleeding. They are weakness, bleeding, headache,
and numbness of the hands and feet.

Blood clots

In primary thrombocythemia, blood clots most often develop in the brain,
hands, and feet. But they can happen anywhere in the body, including in
the heart and intestines.

Blood clots in the brain cause symptoms in 25 percent of people who have
this condition. Common symptoms are chronic (ongoing) headache and dizziness.
In extreme cases, stroke may occur.

Blood clots in the tiny blood vessels of the hands and feet leave them numb
and red. This may lead to an intense burning and throbbing pain felt mainly
on the palms of the hands and the soles of the feet.

Other signs and symptoms of blood clots may include:

Changes in speech or awareness, ranging from confusion to passing
out

Seizures

Upper body discomfort in one or both arms, the back, neck, jaw, or
stomach

Blood clots in the placenta cause fetal death or miscarriage in half of
pregnant women who have primary thrombocythemia.

Blood clots aren't only linked to having thrombocythemia or thrombocytosis,
but to other factors as well. Age (being older than 60), prior blood clots,
diabetes, high
blood pressure, and smoking also increase your risk for blood clots.

Bleeding

Bleeding most often occurs in people who have platelet counts higher than
1 million platelets per microliter of blood. Signs of bleeding include nosebleeds,
bruising, bleeding from the mouth or gums, or blood in the stools.

Although bleeding usually is linked to having a low platelet count, it also
can occur in people who have high platelet counts. Blood clots that develop
in thrombocythemia or thrombocytosis may use up your body's platelets. This
means that not enough platelets are left in your bloodstream to seal off
any cuts and breaks in the blood vessels.

Another cause of bleeding in patients who have very high platelets counts
is a condition called von Willebrand Disease. This condition affects the
blood clotting process.

In rare cases of primary thrombocythemia (less than 2 percent), the faulty
bone marrow cells will cause a form of leukemia
(a cancer of the blood cells).

Secondary thrombocytosis

People who have secondary thrombocytosis have a lower risk for bleeding
and blood clots. This is because their platelets are generally normal (unlike
in primary thrombocythemia) and their platelet counts aren't as high.

However, people who have this condition are at higher risk for blood clots
and bleeding if they're on bed rest or have a severe disease of the arteries.

Diagnosis

Your doctor will diagnose thrombocythemia or thrombocytosis based on your
medical history, a physical exam, and test results. A hematologist also
may be involved in your care. This is a doctor who treats people who have
blood diseases.

Medical history

Your doctor may ask you about factors that can affect your platelets, such
as:

Your general eating habits, including the amount of alcohol you normally
drink

Any family history of high platelet counts

Physical exam

Your doctor will do a physical exam to look for signs and symptoms of bleeding
and blood clots. He or she also will check for signs of conditions that
can cause secondary thrombocytosis, such as infection.

Primary thrombocythemia is diagnosed only after all other possible causes
of a high platelet count are ruled out. For example, your doctor may order
tests to check for early, undiagnosed cancer. If another disease, condition,
or factor is causing a high platelet count, the diagnosis is secondary thrombocytosis.

Diagnostic tests

Your doctor may order one or more of the following tests to help diagnose
a high platelet count.

Complete blood count

A complete blood count (CBC) measures the levels of red blood cells, white
blood cells, and platelets in your blood. For this test, a small amount
of blood is drawn from a blood vessel, usually in your arm.

If you have thrombocythemia or thrombocytosis, the test results will show
that your platelet count is high.

Blood smear

A blood smear is used to check the condition of your platelets. For this
test, a small amount of blood is drawn from a blood vessel, usually in your
arm. Your doctor looks at the blood sample under a microscope.

Bone marrow tests

Bone
marrow tests check whether your bone marrow is healthy. Blood cells,
including platelets, are made in bone marrow. The two bone marrow tests
are aspiration and biopsy.

Bone marrow aspiration may be done to find out whether your bone marrow
is making too many platelets. For this test, your doctor removes a small
amount of fluid bone marrow through a needle. He or she examines the sample
under a microscope to check for faulty cells.

A bone marrow biopsy often is done right after an aspiration. For this test,
your doctor removes a small amount of bone marrow tissue through a needle.
He or she examines the tissue to check the number and types of cells in
the bone marrow. With thrombocythemia and thrombocytosis, the bone marrow
has a higher than normal number of the very large cells that make platelets.

Other tests

Your doctor may order other blood tests to look for genetic factors that
can cause a high platelet count.

Treatment

Primary thrombocythemia

This condition is considered less harmful today than in the past, and its
outlook is often good. People who have no signs or symptoms don't need treatment,
as long as the condition remains stable.

Taking aspirin may help people who are at
risk for blood clots, because aspirin thins the blood. However, you should
talk to your doctor about using aspirin, because it can cause bleeding.
Doctors prescribe aspirin to most pregnant women who have primary thrombocythemia.
This is because it doesn't have a high risk for side effects to the fetus.

Some people who have primary thrombocythemia may need medicines or medical
procedures to lower their platelet counts.

Hydroxyurea. This is the most common platelet-lowering
medicine to treat primary thrombocythemia. Hydroxyurea is used to treat
cancers and other life-threatening diseases. It's most often given under
the care of doctors who specialize in cancer or blood diseases. Patients
on hydroxyurea are closely monitored.

Currently, hydroxyurea plus aspirin is the standard treatment for people
who have primary thrombocythemia and are at high risk for blood clots.

Anagrelide. This medicine has been used to treat thrombocythemia.
However, it seems less effective than hydroxyurea. Anagrelide also has side
effects such as fluid retention, palpitations,
arrhythmias, heart
failure, and headaches.

Interferon alfa.
This medicine is effective at lowering platelet counts. However, 20 percent
of patients can't handle its side effects. These include a flu-like feeling,
decreased appetite, nausea (feeling sick to the stomach), diarrhea,
seizures, irritability, and sleepiness.

Doctors may prescribe this medicine to pregnant women who have primary thrombocythemia.
This is because it's safer for the fetus than hydroxyurea and anagrelide.

Plateletpheresis

Plateletpheresis is a procedure used to rapidly lower your platelet count.
This procedure is only used for emergencies. For example, if you're having
a stroke due to primary thrombocythemia, you may need plateletpheresis.

During this procedure, an intravenous (IV) needle that's connected to a
tube is placed in one of your blood vessels to remove blood. The blood goes
through a machine that removes platelets from the blood. The remaining blood
is then put back into you through an IV line in one of your blood vessels.

One or two procedures may be enough to reduce your platelet count to a safe
level.

Secondary thrombocytosis

People who have this condition usually don't need platelet-lowering medicines
or procedures. This is because their platelets are generally normal (unlike
in primary thrombocythemia). Also, their platelet counts often aren't high
enough to put them at risk for blood clots or bleeding.

Prevention

You can't prevent primary thrombocythemia. However, you can take steps to
reduce your risk for blood clots and prevent related problems.

Age, prior blood clots, diabetes, high blood pressure, high blood cholesterol,
and smoking are all risk factors for blood clots. To reduce your risk, stop
smoking and work to control the risk factors that you can.

It's not always possible to prevent conditions that lead to secondary thrombocytosis.
But, if you have regular medical care, your doctor may find these conditions
before you develop a high platelet count.

Living with thrombocythemia and thrombocytosis

If you have thrombocythemia or thrombocytosis, it's important to:

Get regular medical care.

Stop smoking and control risk factors for blood clots, such as high
blood pressure, diabetes, and high blood cholesterol.

Watch for signs and symptoms of blood clots and bleeding and report
them to your doctor right away.

Take all medicines as prescribed.

If you're taking medicines to lower your platelet count, tell your doctor
or dentist about them before any surgical or dental procedures. These medicines
thin your blood and may increase bleeding during such procedures.

Medicines that thin the blood also may cause internal bleeding. Signs of
internal bleeding include bruises, bloody or tarry-looking stools, pink
or bloody urine, increased menstrual bleeding, bleeding gums, and nosebleeds.
Contact your doctor right away if you have any of these signs.

Avoid over-the-counter pain medicines such as ibuprofen
(except Tylenol®). These medicines may raise your risk for bleeding
in the stomach or intestines and may limit the effect of aspirin. Be aware
that cold and pain medicines and other over-the-counter remedies may contain
ibuprofen.